I you want to grow plants then you will be best off with small gravel or sand. Childens's playpit sand is non-toxic and cheap but will compact over time. You can prevent this with a heater cable running underneath the sand (or gravel), this provides convection currents and allows the substrate to act as a massive biological filter. I installed one after an outbreak of Cyanobacteria.
It's down to personal opinion but I think coloured gravel looks tacky, I think to get the most pleasant effect you're better off simulating nature.
No fish will clean the gravel for you as such. Ground feeders i.e. Corys will perhaps eat leftovers but require a seperate suitable diet. Otos are algae eaters, normally feeding off plants (without harming plant) or aquarium glass. I've heard snails can help with deritus but not too sure.